Culture substrate comprising carbon nanotube structure

ABSTRACT

A culture medium includes a carbon nanotube structure and a hydrophilic layer. The culture medium is capable of culturing at least one neuron. The hydrophilic layer has a polar surface and is located on a surface of the carbon nanotube structure. The polar surface is located on a surface of the hydrophilic layer away from the carbon nanotube structure, and has a polarity attracted to a polarity of the at least one neuron.

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201110031676.3, filed on Jan. 28, 2011 andChina Patent Application No. 201110100912.2, filed on Apr. 21, 2011 inthe China Intellectual Property Office, disclosure of which isincorporated herein by reference.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to commonly-assigned application Ser. No.13/349,582, entitled, “NERVE GRAFT,” filed on Jan. 13, 2012, Ser. No.13/349,577, entitled, “METHOD FOR FORMING NERVE GRAFT,” filed on Jan.13, 2012, and Ser. No. 13/349,660, entitled, “METHOD FOR FORMING CULTUREMEDIUM,” filed on Jan. 13, 2012.

BACKGROUND

1. Technical Field

The present disclosure relates to a culture medium, especially to aculture medium for culturing neurons.

2. Description of Related Art

A nervous system is a complex cellular communication network that ismainly composed of neurons and glial cells (neuroglial cells). Glialcells occupy spaces between the neurons and modulate the neurons'functions. The neurons sense stimuli and transmit this information tothe brain for processing and storage. For example, the neurons receivediverse stimuli from the environment (e.g. light, touch, sound) andtransmit electrical signals, which are then converted into chemicalsignals to be passed on to other cells.

Neurons exist in a number of different shapes and sizes, and can beclassified by their morphology and function. The basic morphology of aneuron includes a cell body and neurites projecting/branching from thecell body towards other neurons. The neurites can also be divided intotwo types by their functions. One is a dendrite, which branches aroundthe cell body and receive signals from other neurons to the cell body.The other is an axon, which branches from the cell body and growscontinually without tapering. The axon conducts the signals away fromthe neuron's cell body. The end of the axon has branching terminals thatrelease neurotransmitters into a gap between the branching terminals andthe dendrites of other neurons. Thus, the information or signal ispropagated.

Neuron damage can lead to neurite degeneration and retraction. If thedamage is severe, breaks in neurites affect signal transmission and thecellular communication between neurons will cease.

What is needed, therefore, is a culture medium for culturing neuronswhich can reconnect opposite terminals in broken neurites.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the drawings. The components in the drawings are not necessarilydrawn to scale, the emphasis instead being placed upon clearlyillustrating the principles of the present disclosure. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a cross-sectional view of one embodiment of a culture medium.

FIG. 2 shows a scanning electron microscope (SEM) image of a flocculatedcarbon nanotube film.

FIG. 3 shows an SEM image of a pressed carbon nanotube film.

FIG. 4 shows an SEM image of a drawn carbon nanotube film.

FIG. 5 shows an SEM image of a carbon nanotube structure.

FIG. 6 shows an SEM image of an untwisted carbon nanotube wire.

FIG. 7 shows an SEM image of a twisted carbon nanotube wire.

FIG. 8 is a flow chart of one embodiment of a method for forming aculture medium.

FIG. 9 is a flowchart of one embodiment of a method for culturing anumber of neurons.

FIG. 10 is a cross-sectional view of another embodiment of a culturemedium.

FIG. 11 is a flow chart of another embodiment of a method for forming aculture medium.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

Referring to FIG. 1, one embodiment of a culture medium 10 includes acarbon nanotube structure 12 and a hydrophilic layer 14. The hydrophiliclayer 14 is located on a surface of the carbon nanotube structure 12.

The hydrophilic layer 14 is a hydrophilic environment for growing anumber of neurons. The thickness of the hydrophilic layer 14 is in arange from about 1 nanometer (nm) to about 100 nm. Preferably, thehydrophilic layer 14 has a thickness in a range from about 1 nm to about50 nm. The hydrophilic layer 14 is made from inorganic materials, suchas silicon dioxide, titanium dioxide, iron oxide, or any combinationthereof. In one embodiment, the hydrophilic layer 14 is a silicondioxide layer with a thickness about 10 nm.

The carbon nanotube structure 12 is capable of forming a free-standingstructure. The term “free-standing structure” can be defined as astructure that does not need to be supported by a substrate. Forexample, a free-standing structure can sustain the weight of itself ifthe free-standing structure is hoisted by a portion thereof without anysignificant damage to its structural integrity. Carbon nanotubesdistributed in the carbon nanotube structure 12 defines a plurality ofgaps therebetween. The carbon nanotubes can have a significant van derWaals attractive force therebetween. The free-standing structure of thecarbon nanotube structure 12 is realized by the carbon nanotubes joinedby van der Waals attractive force.

The carbon nanotubes in the carbon nanotube structure 12 can be orderlyor disorderly arranged. The term ‘disordered carbon nanotube filmstructure’ includes, but is not limited to, a structure where the carbonnanotubes are arranged along many different directions such that thenumber of carbon nanotubes arranged along each different direction canbe almost the same (e.g. uniformly disordered), and/or entangled witheach other. The term ‘ordered carbon nanotube film structure’ includes,but is not limited to, a structure where the carbon nanotubes arearranged in a consistently systematic manner, e.g., the carbon nanotubesare arranged approximately along a same direction and or have two ormore sections within each of which the carbon nanotubes are arrangedapproximately along a same direction (different sections can havedifferent directions). The carbon nanotubes in the carbon nanotubestructure 12 can be single-walled, double-walled, and/or multi-walledcarbon nanotubes.

The carbon nanotube structure 12 can include a flocculated carbonnanotube film as shown in FIG. 2. The flocculated carbon nanotube filmcan include a number of long, curved, disordered carbon nanotubesentangled with each other and can form a free-standing structure.Furthermore, the flocculated carbon nanotube film can be isotropic. Thecarbon nanotubes can be substantially uniformly dispersed in theflocculated carbon nanotube film. The adjacent carbon nanotubes areacted upon by the van der Waals attractive force therebetween, therebyforming an entangled structure with micropores defined therein.Alternatively, the flocculated carbon nanotube film is porous. Sizes ofthe micropores can be in a range from about 1 nm to about 500 nm. Due tothe carbon nanotubes in the carbon nanotube structure 12 being entangledwith each other, the carbon nanotube structure 12 employing theflocculated carbon nanotube film has excellent durability and can befashioned into desired shapes with a low risk to the integrity of thecarbon nanotube structure 12. The flocculated carbon nanotube film, insome embodiments, will not require the use of a structural support dueto the carbon nanotubes being entangled and adhered together by van derWaals attractive force therebetween.

The carbon nanotube structure 12 can include a pressed carbon nanotubefilm. The carbon nanotubes in the pressed carbon nanotube film can bearranged along a same direction or arranged along different directions.The carbon nanotubes in the pressed carbon nanotube film can rest uponeach other. The adjacent carbon nanotubes are combined and attracted toeach other by van der Waals attractive force, and can form afree-standing structure. An angle between a primary alignment directionof the carbon nanotubes and a surface of the pressed carbon nanotubefilm can be in a range from about 0 degrees to about 15 degrees. Thepressed carbon nanotube film can be formed by pressing a carbon nanotubearray. The angle is closely related to pressure applied to the carbonnanotube array. The greater the pressure, the smaller the angle. Thecarbon nanotubes in the carbon nanotube film are substantially parallelto the surface of the carbon nanotube film if the angle is about 0degrees. A length and a width of the carbon nanotube film can be set asdesired. The pressed carbon nanotube film can include a number of carbonnanotubes substantially aligned along one or more directions. Thepressed carbon nanotube film can be obtained by pressing the carbonnanotube array with a pressure head. Alternatively, the shape of thepressure head and the pressing direction can determine the direction ofthe carbon nanotubes arranged therein. Specifically, in one embodiment,a planar pressure head is used to press the carbon nanotube array alongthe direction substantially perpendicular to a substrate. A number ofcarbon nanotubes pressed by the planar pressure head may be sloped inmany directions. In one embodiment, as shown in FIG. 3, if aroller-shaped pressure head is used to press the carbon nanotube arrayalong a certain direction, the pressed carbon nanotube film having anumber of carbon nanotubes substantially aligned along the certaindirection can be obtained. In another embodiment, if the roller-shapedpressure head is used to press the carbon nanotube array along differentdirections, the pressed carbon nanotube film having a number of carbonnanotubes substantially aligned along different directions can beobtained.

In one embodiment, the carbon nanotube structure 12 includes at leastone drawn carbon nanotube film as shown in FIG. 4. The drawn carbonnanotube film can have a thickness of about 0.5 nm to about 100micrometers (μm). The drawn carbon nanotube film includes a number ofcarbon nanotubes that can be arranged substantially parallel to asurface of the drawn carbon nanotube film. A plurality of microporeshaving a size of about 1 nm to about 500 nm can be defined by the carbonnanotubes. A large number of the carbon nanotubes in the drawn carbonnanotube film can be oriented along a preferred orientation, meaningthat a large number of the carbon nanotubes in the drawn carbon nanotubefilm are arranged substantially along the same direction. An end of onecarbon nanotube is joined to another end of an adjacent carbon nanotubearranged substantially along the same direction, by van der Waalsattractive force. More specifically, the drawn carbon nanotube filmincludes a number of successively oriented carbon nanotube segmentsjoined end-to-end by van der Waals attractive force therebetween. Eachcarbon nanotube segment includes a number of carbon nanotubessubstantially parallel to each other and joined by van der Waalsattractive force therebetween. The carbon nanotube segments can vary inwidth, thickness, uniformity, and shape. A small number of the carbonnanotubes are randomly arranged in the drawn carbon nanotube film andhas a small if not negligible effect on the larger number of the carbonnanotubes in the drawn carbon nanotube film arranged substantially alongthe same direction.

In another embodiment, the carbon nanotube structure 12 can include anumber of stacked drawn carbon nanotube films as shown in FIG. 5.Adjacent drawn carbon nanotube films can be adhered by only the van derWaals attractive force therebetween. An angle can exist between thecarbon nanotubes in adjacent drawn carbon nanotube films. The anglebetween the aligned directions of the adjacent drawn carbon nanotubefilms can be in a range from about 0 degrees to about 90 degrees. In oneembodiment, the carbon nanotube structure 12 is formed by 30 layers ofdrawn carbon nanotube films. The angle between the aligned directions ofthe adjacent drawn carbon nanotube films is about 90 degrees.Simultaneously, aligned directions of adjacent drawn carbon nanotubefilms can be substantially perpendicular to each other, thus a pluralityof micropores and nodes can be defined by the carbon nanotube structure12.

Alternatively, the carbon nanotube structure 12 can be formed by anumber of carbon nanotube wires. Thus, one portion of the carbonnanotube wires is arranged substantially parallel to each other andextends substantially along a first direction. In addition, the otherportion of the carbon nanotube wires is arranged substantially parallelto each other and extends substantially along a second direction. Thefirst direction and the second direction can be substantiallyperpendicular to each other. In one embodiment, the carbon nanotube wirecan be classified as untwisted carbon nanotube wire and twisted carbonnanotube wire. Referring to FIG. 6, the untwisted carbon nanotube wireis made by treating an organic solvent to the carbon nanotude filmdescribed above. In such case, the carbon nanotubes of the untwistedcarbon nanotube wire are substantially parallel to the axis of thecarbon nanotube wire. In one embodiment, the organic solvent can beethanol, methanol, acetone, dichloroethane, or chloroform. The diameterof the untwisted carbon nanotube wire is in a range from about 0.5 nm toabout 1 millimeter.

Furthermore, referring to FIG. 7, the carbon nanotube wire can be formedby twisting the carbon nanotube film to form the twisted carbon nanotubewire. Specifically, twisted carbon nanotube wire is formed by turningtwo opposite ends of the carbon nanotube film in opposite directions. Inone embodiment, the carbon nanotubes of the carbon nanotube wire arealigned around the axis of the carbon nanotube spirally.

The culture medium 10 can define a growth surrounding the neurons, thusthe nerve network can be formed on the culture medium 10. Both of thehydrophilic layer 14 and the carbon nanotube structure 12 can have goodtactility, and nonmetal and bio-compatible properties. Thus, the culturemedium 10 including the hydrophilic layer 14 and the carbon nanotubestructure 12 can be transplanted into a biological body and form a shapeas desired. The shape and a thickness of the culture medium 10 can bedesigned as a shape and a thickness of a wound on the biological body.The neurons of the nerve network can communicate with each other, thus,if the culture medium 10 with the nerve network is transplanted into thewound, neurons of the biological body close to the wound can communicatewith and connect to the nerve network. Thus, the injured neurons can bereconnected together. In one embodiment, an area of a surface of thecarbon nanotube structure 12 is greater than 15×15 square millimeters.

Referring to FIG. 8, a method for forming a culture medium includes thesteps of:

S10, providing a carbon nanotube structure; and

S20, forming a hydrophilic layer on a surface of the carbon nanotubestructure

In the step S10, the carbon nanotube structure has a number of carbonnanotubes capable of forming a free-standing structure. Thefree-standing structure of the carbon nanotube structure is realized bythe carbon nanotubes joined by van der Waals attractive force. Thecarbon nanotube structure can include at least one carbon nanotube film.The carbon nanotube film can be a flocculated carbon nanotube film asshown in FIG. 2, a pressed carbon nanotube film as shown in FIG. 2, or adrawn carbon nanotube film as shown in FIG. 4. In addition, the carbonnanotube structure can include at least one carbon nanotube wire. Thecarbon nanotube wire can be an untwisted carbon nanotube wire as shownin FIG. 6 or a twisted carbon nanotube wire as shown in FIG. 7. In oneembodiment, the carbon nanotube structure is formed by 30 layers ofdrawn carbon nanotube films. The angle between the aligned directions ofthe adjacent drawn carbon nanotube films is substantially 90 degrees.

In the step S20, the hydrophilic layer is formed on the surface of thecarbon nanotube structure by evaporation or sputtering. The hydrophiliclayer is capable of culturing a number of neurons. The material of thehydrophilic layer is hydrophilic. For example, the hydrophilic layer ismade from inorganic materials, such as silicon dioxide, titaniumdioxide, iron oxide, or any combination thereof. In one embodiment, thecarbon nanotube structure formed by 30 layers of drawn carbon nanotubefilms is fixed at a frame, and then a silicon dioxide layer is formed onthe surface of the carbon nanotube structure by electron beamevaporation.

The carbon nanotube structure can be sterilized. Sterilizing the carbonnanotube structure kills all of the bacteria distributed in the carbonnanotube structure. The carbon nanotube structure can be sterilized bymeans of an ultraviolet sterilization technology or a high temperaturesterilization technology.

Referring to FIG. 9, a method for culturing a number of neurons includesthe steps of:

S100, providing a culture medium having a carbon nanotube structure anda hydrophilic layer formed on a surface of the carbon nanotubestructure;

S200, polarizing the hydrophilic layer to form a polar surface on thehydrophilic layer;

S300, seeding a number of neurons on the polar surface of thehydrophilic layer; and

S400, culturing the neurons.

In the step S200, the polar surface can be formed on the hydrophiliclayer by the steps of:

(a1), providing a supporter;

(b1), placing the carbon nanotube structure having the hydrophilic layeron a surface of the supporter; and

(c1), forming the polar surface on the hydrophilic layer by soaking thecarbon nanotube structure having the hydrophilic layer on the supporter.

In step (b1), the carbon nanotube structure can be located on part ofthe surface of the supporter. To decrease a specific surface area of thecarbon nanotube structure and increase an adhesive attraction forcebetween the carbon nanotube structure and the supporter, the step (b1)can further include the following steps: (b11), soaking the carbonnanotube structure on the surface of the supporter with an organicsolvent; and (b12), evaporating the organic solvent from the carbonnanotube structure. In one embodiment, the supporter is a plastic petridish or an observation dish.

In step (c1), the carbon nanotube structure can be soaked with apolyamino acid solution or a polyetherimide solution to form the polarsurface on the hydrophilic layer. For example, the polyamino acidsolution or the polyetherimide solution can be sprayed on the surface ofthe hydrophilic layer. In one embodiment, to soak the hydrophilic layerwith the polyamino acid solution or the polyetherimide solution, thestep (c1) includes the following steps: (c11), dripping the polyaminoacid solution or the polyetherimide solution on the surface of thehydrophilic layer; and (c12), purging the polyamino acid solution or thepolyetherimide solution from the hydrophilic layer with deionized waterafter the polar surface is formed on the hydrophilic layer. In oneembodiment, the polyamino acid solution is dripped on the carbonnanotube structure for about 10 hours. A concentration of the polyaminoacid solution can be about 20 milligrams per milliliter.

In the step S300, the neurons can be from a mammal, such as a human, amouse, or a cow. In one embodiment, the neurons are hippocampal neuronsfrom a mouse. The neurons can be seeded on the hydrophilic layer byspraying a neuron solution to the polar surface of the hydrophiliclayer, or by dipping the culture substrate into the neuron solution. Inone embodiment, when the polar surface of the hydrophilic layer iscovered by the neuron solution, the neurons in the neuron solution canbe deposited or seeded on the polar surface of the hydrophilic layer.

Referring to FIG. 10, one embodiment of a culture medium 20 includes acarbon nanotube structure 12, a hydrophilic layer 14, and a polar layer26. The hydrophilic layer 14 is located on a surface of the carbonnanotube structure 12. The polar layer 26 is located on a surface of thehydrophilic layer 14 away from the carbon nanotube structure 12. Inother words, the hydrophilic layer 14 is located between the carbonnanotube structure 12 and the polar layer 26.

The hydrophilic layer 14 makes the carbon nanotube structure 12 ahydrophilic environment for growing a number of neurons. In addition,the hydrophilic layer 14 makes the polar layer 26 adhere easily to thecarbon nanotube structure 12. The thickness of the hydrophilic layer 14is in a range from about 1 nanometer (nm) to about 100 nm. Preferably,the hydrophilic layer 14 has a thickness in a range from about 1 nm toabout 50 nm. The hydrophilic layer 14 is made from inorganic materials,such as silicon dioxide, titanium dioxide, iron oxide, or anycombination thereof. In one embodiment, the hydrophilic layer 14 is asilicon dioxide layer with a thickness about 10 nm.

The polar layer 26 is capable of providing a polarity such that thepolarity of the culture medium 10 can attract the neurons. Thus, theculture medium 10 is capable of providing a bio-compatible environmentfor seeding the neurons and forming a nerve network. The surface of theculture medium 10 with a polarity will attract another polarity of asurface of the nerve network with the opposite affinity. Thus, the nervenetwork can closely adhere to the surface of the culture medium 10. Amaterial of the polar layer 26 can be polyamino acid, polyetherimide,and any combination thereof. The polyamino acid can be poly-D-lysine(PDL). In one embodiment, the polar layer 26 is a PDL layer.

Referring to FIG. 11, a method for forming a culture medium includes thesteps of:

S11, providing a carbon nanotube structure;

S21, forming a hydrophilic layer on a surface of the carbon nanotubestructure; and

S31, forming a polar layer on a surface of the hydrophilic layer to formthe culture medium.

In the step S11, the carbon nanotube structure has a number of carbonnanotubes capable of forming a free-standing structure. Thefree-standing structure of the carbon nanotube structure is realized bythe carbon nanotubes joined by van der Waals attractive force. Thecarbon nanotube structure can include at least one carbon nanotube film.The carbon nanotube film can be a flocculated carbon nanotube film asshown in FIG. 2, a pressed carbon nanotube film as shown in FIG. 2, or adrawn carbon nanotube film as shown in FIG. 4. In addition, the carbonnanotube structure can include at least one carbon nanotube wire. Thecarbon nanotube wire can be an untwisted carbon nanotube wire as shownin FIG. 6 or a twisted carbon nanotube wire as shown in FIG. 7. In oneembodiment, the carbon nanotube structure is formed by 30 layers ofdrawn carbon nanotube films. The angle between the aligned directions ofthe adjacent drawn carbon nanotube films is substantially 90 degrees.

In the step S21, the hydrophilic layer is formed on the surface of thecarbon nanotube structure by evaporation or sputtering. The material ofthe hydrophilic layer is hydrophilice. For example, the hydrophiliclayer is made from inorganic materials, such as silicon dioxide,titanium dioxide, iron oxide, or any combination thereof. In oneembodiment, the carbon nanotube structure formed by 30 layers of drawncarbon nanotube films is fixed at a frame, and then a silicon dioxidelayer is formed on the surface of the carbon nanotube structure byelectron beam evaporation.

In the step S31, the polar layer can be formed on the surface of thehydrophilic layer by the steps of:

(a1), providing a supporter;

(b1), placing the carbon nanotube structure having the hydrophilic layeron a surface of the supporter; and

(c1), forming the polar layer on the carbon nanotube structure bysoaking the carbon nanotube structure having the hydrophilic layer onthe supporter.

In step (b1), the carbon nanotube structure can be located on part ofthe surface of the supporter. To decrease a specific surface area of thecarbon nanotube structure and increase an adhesive attraction forcebetween the carbon nanotube structure and the supporter, the step (b1)can further include the following steps: (b11), soaking the carbonnanotube structure on the surface of the supporter with an organicsolvent; and (b12), evaporating the organic solvent from the carbonnanotube structure. In one embodiment, the supporter is a plastic petridish or a watch dish.

In step (c1), the carbon nanotube structure can be soaked with apolyamino acid solution or a polyetherimide solution to form the polarlayer. For example, the polyamino acid solution or the polyetherimidesolution can be sprayed on the surface of the hydrophilic layer. In oneembodiment, to soak the hydrophilic layer with the polyamino acidsolution or the polyetherimide solution, the step (c1) includes a stepof dripping the polyamino acid solution or the polyetherimide solutionon the carbon nanotube structure having the hydrophilic layer on thesupporter. In one embodiment, the polyamino acid solution is dripped onthe carbon nanotube structure for about 10 hours. A concentration of thepolyamino acid solution can be about 20 milligrams per milliliter.

The carbon nanotube structure having the polar layer can be furthersterilized. Sterilizing the carbon nanotube structure having the polarlayer kills nearly all of the bacteria distributed in the carbonnanotube structure. The carbon nanotube structure can be sterilized bymeans of an ultraviolet sterilization technology or a high temperaturesterilization technology.

The culture medium including a carbon nanotube structure has thefollowing benefits. First, the hydrophilic layer covers the surface ofthe carbon nanotube structure such that the culture medium has goodhydrophilic property. Second, the carbon nanotube structure is capableof accommodating many different shapes. Third, both of the hydrophiliclayer and the carbon nanotube structure can have good tactility, andnonmetal and bio-compatible properties. Thus, the culture mediumincluding the hydrophilic layer and the carbon nanotube structure can betransplanted into a biological body and form a shape as desired.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the disclosure. Any elements describedin accordance with any embodiments is understood that they can be usedin addition or substituted in other embodiments. Embodiments can also beused together. Variations may be made to the embodiments withoutdeparting from the spirit of the disclosure. The above-describedembodiments illustrate the scope of the disclosure but do not restrictthe scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A culture substrate, comprising: a carbonnanotube structure comprising a pressed carbon nanotube film comprisinga plurality of carbon nanotubes, an angle between a primary alignmentdirection of the carbon nanotubes and a surface of the pressed carbonnanotube film is about 15 degrees, and the carbon nanotube structure isa free-standing structure; a hydrophilic layer directly located on asurface of the carbon nanotube structure, wherein the hydrophilic layeris configured to culture a plurality of neurons thereon such that thehydrophilic layer is located between the carbon nanotube structure andthe plurality of neurons, a material of the hydrophilic layer is aninorganic material selected from the group consisting of silicondioxide, titanium dioxide, iron oxide, and any combination thereof, andthe hydrophilic layer has a thickness in a range from about 1 nm toabout 50 nm; and a polar layer located on a surface of the hydrophiliclayer away from the carbon nanotube structure, wherein the polar layeris made of polyetherimide.
 2. The culture substrate of claim 1, whereinthe carbon nanotube structure comprises at least one untwisted carbonnanotube wire.
 3. The culture substrate of claim 1, wherein an area ofthe surface of the carbon nanotube structure is greater than 15×15square millimeters.